Technical Field
The disclosure relates in general to a compensation apparatus and an inductor-based apparatus, and more particularly to a compensation apparatus and an inductor-based apparatus with temperature compensation function.
Description of the Related Art
Phase-locked loop (hereinafter, PLL) circuits are widely used for the distribution of clocks on microprocessors, digital signal processors (DSPs), field programmable gate arrays (FPGAs), etc. In a PLL circuit, a voltage-controlled oscillator (hereinafter, VCO) is the key analogue block to determine the frequency stability and the jitter performance.
In current technology, LC VCO is a widely used scheme for CMOS based VCO design. The oscillation frequency of a LC VCO is determined by the resonator inductor and capacitor. However, the oscillation frequency of the LC VCO is temperature dependent. Factors such as changes of inductance, changes of Q factor of the inductance, swing amplitude of the VCO itself, or non-linear capacitance etc. cause variations of the oscillation frequency of LC VCO over temperature. Consequentially, techniques for temperature compensation should be utilized to improve the accuracy of the oscillation frequency.
Techniques for compensating for the effects of temperature change on VCO frequency are developed. The conventional temperature compensation circuits utilize varactors to provide a negative temperature coefficient (TC) to the LC VCO. With the negative temperature coefficient, the frequency drift caused by temperature variation is eliminated. However, the varactors may occupy significant silicon area. Therefore, a more economic approach for TC compensation is required.